Are changes in solar activity causing climate change?

The rise in global temperatures over the past century cannot be explained by the small changes in the sun’s energy output.

The sun varies slightly in brightness through several natural cycles, including an 11-year sunspot cycle, but these shifts are small and largely cancel out over decades. Satellite measurements show total solar irradiance actually drifted slightly downward since the late 1970s, which would have caused mild cooling, not rapid warming.

Over longer timescales, research has found that solar changes account for 1% of the 1.4°C (2.5°F) of warming since pre-industrial times. In contrast, greenhouse gas emissions from burning fossil fuels cause far more warming and align closely with the measured temperature rise.

Change in the sun’s activity has been small and cannot explain the recent rise in global temperatures. The dominant driver of today’s climate change is not the sun, but greenhouse gas emissions from our use of fossil fuels.